For lung cancer - yep - banning smoking would not only massively reduce the rates, but also other lung diseases - China is heading for an absolute epidermic here.

However, for those people that have or are going to get lung cancer or diabetes or other generally ( not always ) 'self-inflicted' diseases - should we just say - sorry - no treatment - it's you're own silly fault?

For heart disease - actually the best treatments are effectively preventative already - in cancer HPV vaccine is aimed at reducing cervical cancer - I've worked with the inventors of that.

In terms of 'whataboutery' of should you be spending money on rich peoples diseases ( whether self inflicted or not ), when you could save more lives in other countries with basic sanitation.

Well that's a whole different question - a question for collective action through governments or charity - not a question for commercial companies. Commercial companies have to find people able to pay for what they do ( which could be governments or charities ).

Personally I don't see why it needs to be either/or - ie why we can't we work on both cure's for cancer and provide clean water?